Typically on motor homes and travel trailers the main entrance door leading into the living quarters and other restricted areas is secured with a latch equipped with a locking mechanism that can be operated from inside or outside the vehicle.
It is common practice to have large numbers of these locks all keyed alike. The reason for this is to reduce the number of different keys the manufacturer and dealer have to contend with while the vehicle is in their possession. It is more convenient for a dealer to unlock a number of vehicles with one master key when showing to customers than to locate and carry around a separate set of keys for each vehicle on the lot.
Unfortunately this practice offers very little security against unauthorized entrance into the motor home, so in addition to the locking door latch a separate dead bolt is installed in each door. The dead bolt is designed to be keyed to a higher number of key configurations, to reduce the chance of a key from one motor home being able to unlock the dead bolt of the door of another.
The dead bolt can be kept unlocked while on the dealers lot so he can enter any vehicle with a master key, yet the additional security is available for the final owner when required.
This arrangement of a latch bolt lock and a separate dead bolt lock appears to offer the easy access needed by the dealer and the security and peace of mind required by the final owner of the vehicle, but creates other problems in the way of added costs for the additional security.
Having to install two separate units in each door means higher costs, due to the additional labor and materials required for the additional inventory, door preparation and installation, all of which is paid for by the customer in the way of higher product cost.